Google OA Mock Interview Social media question

src/main/java/datastructures/Event.java

@@ -0,0 +1,38 @@
+package datastructures;
+
+public class Event {
+
+    int timestamp;
+    String category;
+    String displayTest;
+
+    public Event(int timestamp, String category, String displayTest) {
+        this.timestamp = timestamp;
+        this.category = category;
+        this.displayTest = displayTest;
+    }
+
+    public int getTimestamp() {
+        return timestamp;
+    }
+
+    public void setTimestamp(int timestamp) {
+        this.timestamp = timestamp;
+    }
+
+    public String getCategory() {
+        return category;
+    }
+
+    public void setCategory(String category) {
+        this.category = category;
+    }
+
+    public String getDisplayTest() {
+        return displayTest;
+    }
+
+    public void setDisplayTest(String displayTest) {
+        this.displayTest = displayTest;
+    }
+}

src/main/java/googleOA/socialMedia/SocialMedia.java

@@ -0,0 +1,42 @@
+package googleOA.socialMedia;
+
+import datastructures.Event;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+public class SocialMedia {
+
+    Map<String, Integer> categoryLimit =
+            Map.of("USER_FOLLOW", 1, "TRENDING_TOPIC", 2, "DIRECT_MESSAGE", 5);
+    public List<String> collapseEvents(List<Event> events) {
+        List<String> res = new ArrayList<>();
+        String previousCategory = null;
+        int previousCategoryCount = 0;
+
+        for (Event event : events) {
+            if (event.getCategory().equals(previousCategory))
+                previousCategoryCount++;
+            else {
+                if (previousCategory != null) {
+                    if (categoryLimit.containsKey(previousCategory)) {
+                        if (previousCategoryCount > categoryLimit.get(previousCategory)) {
+                            String val = previousCategory + "(+" + String.valueOf(previousCategoryCount - 1) + " more)";
+                            res.add(val);
+                        } else {
+                            for (int i = 0; i < previousCategoryCount; i++) {
+                                res.add(previousCategory);
+                            }
+                        }
+                    }
+                }
+                previousCategoryCount = 1;
+            }
+            previousCategory = event.getCategory();
+            if (previousCategoryCount == 0) previousCategoryCount++;
+        }
+
+        return res;
+    }
+}

src/test/java/googleOA/socialMedia/SocialMediaTest.java

@@ -0,0 +1,57 @@
+package googleOA.socialMedia;
+
+import datastructures.Event;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class SocialMediaTest {
+
+    private SocialMedia socialMedia;
+
+    private List<Event> testcase = new ArrayList<>();
+
+    @BeforeEach
+    void setUp() {
+        socialMedia = new SocialMedia();
+        Event first = new Event(1, "USER_FOLLOW", "");
+        Event sec = new Event(1, "USER_FOLLOW", "");
+        Event third = new Event(1, "TRENDING_TOPIC", "");
+        Event fourth = new Event(1, "TRENDING_TOPIC", "");
+        Event fifth = new Event(1, "TRENDING_TOPIC", "");
+        Event sixth = new Event(1, "TRENDING_TOPIC", "");
+        Event seventh = new Event(1, "TRENDING_TOPIC", "");
+        Event eighth = new Event(1, "TRENDING_TOPIC", "");
+        Event nineth = new Event(1, "TRENDING_TOPIC", "");
+        Event tenth = new Event(1, "DIRECT_MESSAGE", "");
+        Event eleventh = new Event(1, "DIRECT_MESSAGE", "");
+        Event twelveth = new Event(1, "DIRECT_MESSAGE", "");
+        Event thirteenth = new Event(1, "DIRECT_MESSAGE", "");
+        Event fourteenth = new Event(1, "DIRECT_MESSAGE", "");
+        Event fifteenth = new Event(1, "DIRECT_MESSAGE", "");
+        Event sixteenth = new Event(1, "TRENDING_TOPIC", "");
+
+        testcase = List.of(first, sec, third, fourth, fifth, sixth, seventh, eighth,
+                nineth, tenth, eleventh, twelveth, thirteenth, fourteenth, fifteenth, sixteenth);
+    }
+
+    @Test
+    void collapseEvents() {
+        List<String> expectedResult = List.of(
+                "USER_FOLLOW",
+                "USER_FOLLOW",
+                "TRENDING_TOPIC (+6 more)",
+                "DIRECT_MESSAGE (+5 more)",
+                "TRENDING_TOPIC"
+        );
+
+        List<String> actualResult = socialMedia.collapseEvents(testcase);
+        for (int i = 0; i < actualResult.size(); i++) {
+            assertEquals(expectedResult.get(i), actualResult.get(i));
+        }
+    }
+}